Unbound excited states of theN=16closed shell nucleusO24

Abstract

Two low-lying neutron-unbound excited states of $^{24}\mathrm{O}$, populated by proton-knockout reactions on $^{26}\mathrm{F}$, have been measured using the MoNA and LISA arrays in combination with the Sweeper Magnet at the Coupled Cyclotron Facility at the NSCL using invariant mass spectroscopy. The current measurement confirms the separate identity of two states with decay energies 0.51(5) MeV and 1.20(7) MeV, and provides support for theoretical model calculations, which predict a ${2}^{+}$ first excited state and a ${1}^{+}$ higher-energy state. The measured excitation energies for these states, 4.70(15) MeV for the ${2}^{+}$ level and 5.39(16) MeV for the ${1}^{+}$ level, are consistent with previous lower-resolution measurements, and are compared with five recent model predictions.